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Tutorial

This lesson will focus muscle contractions from a macro view by examining:

Muscle Groups

Origin and Insertion

1. Muscle Groups

We will continue using our biceps and triceps as our example for how skeletal muscles interact with our skeleton to allow for movement.The bicep and tricep are arranged in a pair working antagonistically to one another. This means that the action of one muscle opposes the action of the other and this is allowed for by something called reciprocal innervation. Reciprocal innervation acts on groups of muscles, so that when one muscle contracts, no signals are sent by the nervous system to the opposing muscle; it relaxes. Reciprocal innervation also allows for the protection of joints, areas where bones come together.

When the bicep contracts, the tricep relaxes because your nervous system is not sending any signals to your tricep. vise versa, when the tricep contracts, the bicep relaxes.

Antagonistic contraction

When an opposing muscle on the opposite side of a joint contracts to create an opposing movement to its muscle counterpart (example flexion vs. extension).

Reciprocal innervation

The nervous system controlling muscle groups that oppose and work against one another; allows for a variety of movements and protection of joints.

Joint

An area where two or more bones come together.

Another type of muscle group are synergistic muscles. Instead of opposing reactions, these muscle groups are working together to increase the force or to stabilize another muscle in the body.

2. Origin and Insertion

Our muscles, our bones, and our tendons, which is a dense connective tissue that attaches bone to muscle, working together to act like a series of levers in order to allow for our skeleton to be able to move. Look at our diagram below to describe origin and insertion.

So origin is the end of a muscle that attaches to a stable bone, while the insertion is the end of a muscle that attaches to a bone that moves.

Origin

The fixed, non-moveable end of a skeletal muscle

Insertion

The fixed, moveable end of a skeletal muscle.

Tendon

A tough band of fibrous connective tissue that usually connects muscle to bone.

Looking at our bicep, the origin is going to be our scapula. This is the stable bone, so when your bicep contracts or relaxes, your scapula is not going to move. Our forearm is what does move when our biceps contracts or relaxes, so that would be our insertion.

There are two different types of muscle groups that work together to allow for movement, stabilize joints, and even stabilize each other. One type of muscle group is when muscles work antagonistically to each other. This means when one muscle contracts the other relaxes. The other type of group is synergistic muscles. These muscles work together at the same time to increase force. Skeletal muscles connect to bone or other muscles at the origin and insertion. The origin is the part of the muscle that connects to a stable bone, while the insertion attaches to a bone that will move.

Keep up the learning and have a great day!

Source: Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW

Tendon

A tough band of fibrous connective tissue that usually connects muscle to bone.

Origin

The fixed, non-moveable end of a skeletal muscle

Insertion

The fixed, moveable end of a skeletal muscle.

Joint

An area where two or more bones come together.

Antagonistic contraction

When an opposing muscle on the opposite side of a joint contracts to create an opposing movement to its muscle counterpart (example flexion vs. extension).

Synergistic contraction

When a group of muscles work together to create the same movement; an example would be your bicep brachii and brachialis muscle contraction simultaneously to create flexion (bending) of your elbow.

Reciprocal innervation

The nervous system controlling muscle groups that oppose and work against one another; allows for a variety of movements and protection of joints.